Hybrid injector



March 28, 1967 R. MATTHEWS HYBRID INJECTOR Filed March 29, 1965 FIG.

FIG.

FIG. 2A.

INVENTOR. FIG 2B DONALD R. MATTHEWS BY V. C. MULLER ATTORNEY.

United States Patent 3,310,950 HYBRID INJECTOR Donald R. Matthews, San Jose, Calif., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Mar. 29, 1965, Ser. No. 443,723 4 Claims. (Cl. 60-251) This invention relates to gas producing motors of the hybrid type which combust a solid and liquid propellant, and more particularly to improvements in method and apparatus for injecting the liquid propellant.

It has been conventional practice to inject a liquid propellant, such as the oxidant, into the central aperture or port of a solid internal burning grain, such as the fuel, by spray nozzles located at the front end of the motor which spray the liquid into the port in a predetermined spray pattern, as determined by the spray nozzle configuration. As the inner surface of the solid grain burns, increasing the diameter of the port, the spray pattern, if optimum at the beginning of burning, for example, may no longer be optimum at a later stage of burning. This has resulted in localized burning of the grain, rather than the desired uniform burning which would consume the final annular portion of the grain at substantially the same time. As will be apparent, this erractic and non-uniform burning renders predicted performance difiicult, and in some instances may cause rupture of the motor tube, due to premature exposure to the hot gasses, before the solid grain is entirely consumed.

One of the objects of this invention is to obviate the disadvantages of the prior art referred to by the provision of novel apparatus for, and method of, injecting a liquid propellant in a varying injection pattern as the central port of the solid grain increases in diameter, to thereby optimize the injection during the entire burning period of the propellant.

Another object is to provide injection apparatus of simplified construction, and without movable parts or valves, wherein the decreasing annular end area of the solid grain provides an automatic valve for opening additional liquid supply apertures.

Still further objects, advantages and salient features will become more apparent from the description to follow, the appended claims, and the accompanying drawing, in which:

FIG. 1 is a longitudinal central section through a gas producing motor, employing the subject of the invention, at the beginning of the combustion process;

FIG. 1A is a like section near the end of the combustion process;

FIG. 2 is an enlarged section taken on line 22 of FIG. 1, and

FIGS. 2A and 2B are end elevations, as viewed in the direction of arrow 2, FIG. 1, of alternative forms of foraminous disks which may be employed in FIGS. 1 and 1A.

Referring now to the drawing, motor tube is of any conventional construction, having a nozzle 12 at its rear end and a closure 14 at its front end and containing a solid propellant grain 16, having an axial perforation or port 18. The grain may be suitably inhibited from burning (not shown) at its outer surface, as well known in ice the art, and is commonly referred to as an internal buming grain.

The novel injection apparatus comprises a circular foraminous disk 20, preferably of high heat resisting material, such as stainless steel, which is disposed adjacent the front annular face of the grain and sealed to the same so that liquid propellant may pass only through the portion of the honeycomb which is not covered by the grain, that is, the portion surrounded by the periphery of port 18. As shown in FIG. 2, foraminous disk 20 may be of honeycomb material 20a, a drilled disk 20b as shown in FIG. 2A, or one or more stacked woven screens 200 as shown in FIG. 2B. The apertures would normally beuniformly spaced in any of these alternative forms of disks, however, the drilled type of disk could, if desired, have non-uniformly spaced apertures to control fluid flow rate through the same in a desired rate of flow pattern. In FIG. 1, illustrating commencement of combustion, liquid propellant may fiow through a relatively small portion of disk 20 and in FIG. 1A, illustrating a later stage of combustion, the liquid propellant may flow through a considerably larger portion. At any stage of combustion, the liquid propellant flows axially of the grain and with an outlet area proportional to, but somewhat smaller than the cross sectional area of the port. Since the liquid propellant in the annular portion of the disk surrounding aperture 18 is in contact with the annular unburned end of the disk, and since no reaction between such end and the liquid can take place if the disc is to serve as a valve, as described, it is apparent that the liquid and the grain cannot be of the hypergolic type, and that the only place combustion must take place is within port 18. Being of non-hypergolic type, is also apparent that combustion must be initiated by an igniter (not shown), such mode of initiation being well known in the art. Supply of the liquid propellant is through a pipe 22 communicating with a chamber or manifold 24 adjacent the forward face of the honeycomb.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In a hybrid bi-propellant rocket motor of the type wherein one of the propellants is a solid cylindrical grain having a central port extending between opposite ends thereof and the other propellant is a liquid adapted to be injected axially of the port, the improvements, in combination, comprising:

a) A circular nozzle disk abutting the annular end surface at the front end of the grain having apertures extending therethrough, spaced throughout its entire area, a plurality of which communicate with said port at the commencement of combustion and the surrounding remainder are blocked from communication by the annular end surface of the grain, said remainder adapted to progressively communicate with the port as it enlarges in diameter as the annular surface reduces in area, whereby the number of apertures communicating with said port continuously increases substantially in proportion to the increase in the cross sectional area of said port,

(b) a space of constant size disposed adjacent said disk 3,310,950 3 4 forming a manifold communicating with all of the apertures are hexagonal in cross-section, formed by a apertures at all times during the combustion, and honeycomb material.

(c) means for delivering the liquid propellant to said 4. Apparatus in accordance with claim 1 wherein said manifold for axial flow of the liquid through the apertures are circular in cross section. apertures as they are progressively unblocked by the 6 decreasing annular end surface of the grain. References Cited by the Examiner 2. Apparatus in accordance with claim 1 wherein said UNITED STATES PATENTS apertures are square in cross section, formed by a Wove 1,378,866 10/1964 Moutet 60 251 screen material.

3. Apparatus in accordance with claim 1 wherein said 10 CARLTON R. CROYLE, Primary Examiner. 

1. IN A HYBRID BI-PROPELLANT ROCKET MOTOR OF THE TYPE WHEREIN ONE OF THE PROPELLANTS IS A SOLID CYLINDRICAL GRAIN HAVING A CENTRAL PORT EXTENDING BETWEEN OPPOSITE ENDS THEREOF AND THE OTHER PROPELLANT IS A LIQUID ADAPTED TO BE INJECTED AXIALLY OF THE PORT, THE IMPROVEMENTS, IN COMBINATION, COMPRISING: (A) A CIRCULAR NOZZLE DISK ABUTTING ANNULAR END SURFACE AT THE FRONT END OF THE GRAIN HAVING APERTURES EXTENDING THERETHROUGH, SPACED THROUGHOUT ITS ENTIRE AREA, A PLURALITY OF WHICH COMMUNICATE WITH SAID PORT AT THE COMMENCEMENT OF COMBUSTION AND THE SURROUNDING REMAINDER ARE BLOCKED FROM COMMUNICATION BY THE ANNULAR END SURFACE OF THE GRAIN, SAID REMAINDER ADAPTED TO PROGRESSIVELY COMMUNICATE WITH THE PORT AS IT ENLARGES IN DIAMETER AS THE ANNULAR SURFACE REDUCES IN AREA, WHEREBY THE NUMBER OF APERTURES COMMUNICATING WITH SAID PORT CONTINUOUSLY INCREASES SUBSTANTIALLY IN PROPORTION TO THE INCREASE IN THE CROSS SECTIONAL AREA OF SAID PORT, (B) A SPACE OF CONSTANT SIZE DISPOED ADJACENT SAID DISK FORMING A MANIFOLD COMMUNICATING WITH ALL OF THE APERTURES AT ALL TIMES DURING THE COMBUSTION, AND (C) MEANS FOR DELIVERING THE LIQUID PROPELLANT TO SAID MANIFOLD FOR AXIAL FLOW OF THE LIQUID THROUGH THE APERTURES AS THEY ARE PROGRESSIVELY UNBLOCKED BY THE DECREASING ANNULAR END SURFACE OF THE GRAIN. 